Atomic Number and Orbital Energy Levels
When an electron reaches a given energy level, it is more likely to be located in certain parts of that level than in others. These parts are known as orbitals. Sublevels are formed by orbitals with the same energy. Each orbital may hold a maximum of two electrons.
Drawing diagrams like the one above is the most frequent means of depicting the distribution of electrons in an atom.
Atomic Number
Atomic number of an element refers to the number of protons present in its nucleus. It’s also called the nuclear charge number and is symbolized by Z. In a nonionized atom, the atomic number equals the number of orbiting electrons.
The atomic number defines the identity of an element. For instance, carbon, with six protons, remains a carbon atom irrespective of how many neutrons it has neutron. The atomic number serves as the unique identifier for each element.